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Silicon wafer with micro- and nanostructures
Institute of Microsystems Technology

Fabrication of microstructures on a silicon wafer

For many years, the Institute of Microsystems Technology (iMST) has been researching new microsystems, associated modeling and manufacturing processes, and characterisation methods. The iMST is one of the largest research institutes at HFU, and the research results are also recognised internationally.

Today, microsystems are used by the millions in automobiles (sensors), in communication technology (microphones and high-frequency components, smartphones, micromirrors in projectors, print heads in inkjet printers) and in medical technology (retina implants, cochlear implants). This requires structures in the range of micrometers, which are produced by microtechnical processes and combine electronic and non-electronic functions in a very small space in one system.

The highly motivated, multidisciplinary team conducts research in numerous cooperation projects with companies, scientific institutions and universities on application-oriented issues in microsystems technology.

Research Areas

The Institute of Microsystems Technology has several primary research areas:

 

Functional coatings

Functional coatings

Processed surface to create the lotus effect
Lotus effect on hydrophobic surface

Lotus effect on hydrophobic surface

Functional surfaces help to adapt materials to their environment without changing the volume properties. On the one hand, the surface can be adjusted to be hydrophobic/oleophobic or hydrophilic/oleophilic, but the interaction in physiological environments (biocompatibility) can also be tailored by thin coatings with layer thicknesses in the nanometer to micrometer range. Another field of application is the barrier against diffusion of gases or liquids. Thin coatings can thus also be used to protect mechanically flexible components or active implants against harsh environments. In particular, if the electronics to be protected have DC voltage potentials, a 100% protective effect against corrosion is essential. The miniaturisation of medical devices also increasingly demands high-voltage-resistant and biocompatible insulation coatings with small layer thicknesses.

The following coatings are possible at the institute:

  • physical vapor deposition (PVD)
  • plasma-enhanced chemical vapor deposition (PECVD)
  • (optionally plasma assisted) atomic layer deposition ((PE)ALD)
  • thermal oxidation
  • electroplating
  • spin coating
  • deposition of parylene

The homogeneous, defect-free coating of complex geometries is a particular focus of research and development at the institute. In addition to the coating methods, there are also extensive possibilities for validating the homogeneity, defect-free nature and stability of the deposited layers after exposure to thermal, chemical and cyclic mechanical stress.

 

Micro- and Nanostructuring processes

Micro- and Nanostructuring processes

The ability to produce structures in the micrometer (1 µm = 10⁻⁶ m) to nanometer (1 nm = 10⁻⁹ m) size range is one of the core competencies in microsystems technology and thus also in iMST. The structuring is usually carried out in a two-stage process, in which the structures are first created in a photosensitive lacquer by means of photolithography and these are then subsequently transferred to the underlying thin film by means of etching technology ("negative structuring") or are formed, for example, by electroplating ("additive structuring"). Smallest structures down to 0.6 µm (lateral dimension) and tolerances of about +10% can be generated at iMST by mask-bound photolithography and laser direct writing. As etching techniques for the second structuring step, in which the photoresist structures are transferred into the thin film, various wet chemical processes are available for highly selective etching as well as for highest demands on the structure quality Reactive Ion Etching (RIE) with high anisotropy.

A special field of research at iMST is the fabrication of quasi 3D microstructures by means of the so-called "Grayscale technology", for which three different processes are investigated at iMST. Structure heights or depths of typically up to 50 µm can be produced here.

For the nanostructuring of silicon, research is being conducted on the generation of self-organised nanostructures by electrochemical anodising of silicon (porous silicon). Through targeted nanostructuring, multilayers with a precisely adjusted refractive index can be produced as optical filter layers in the visible to the MIR (mid-infrared) range. These porous layers are also used at iMST for various sensor principles.

An ns laser (Nd:YAG, wavelength of 1064 nm) is available for direct structuring of thin films (e.g. 50 µm thick), but this can only produce structures in the size range above 20 µm.

Development of miniaturised sensors and actuators

Development of miniaturised sensors and actuators

Miniaturised sensors and actuators are examples of microsystems and are used billions of times today in cars or even in smartphones. The iMST has many years of expertise in the development of micromechanical sensors and actuators (so-called MEMS sensors and actuators), primarily based on the material silicon. This also includes optical systems, which can be used e.g. for focusing, in laser scanners or for filtering light, for which actuator functions are used in each case. In recent years, many research projects at iMST have been concerned with flexible sensor-actuator systems based on polymers. The field of application is mostly in medical technology. SOI (silicone on insulator) is mostly used as a technology platform.

In addition to the described competence in the field of micro- and nanostructuring technology, so-called finite element methods are used for the targeted development of sensor and actuator systems, with which very different physical problems and systems can be simulated.  By using this so-called "multiphysics simulation", complex test procedures that have to be run several times can be largely avoided and sensor and actuator prototypes can be realised in a prototypically targeted manner on the basis of specified requirements.

Examples of sensors developed in recent years:

  • MEMS tilt sensors
  • Sound dosimeters for hearing protection
  • Refractometers for the determination of the refractive index of liquids
  • Sensors for insitu detection of burn marks during grinding
  • Sensors for characterisation of vessel properties

Examples of actuators developed at iMST:

  • active focusing systems
  • tactile displays
  • systems for laser scanners
  • inchworm actuators realised
  • bistable micromechanical switches

An important issue in the use of sensor-actuator systems is the energy supply. At m iMST, research is being conducted on Energy Harvesting, in which the systems draw their energy from the environment, and on special forms of electrochemically stored energy. Telemetric energy supply is also being investigated.

Surface and interface analysis

Surface and interface analysis

Barrier layer produced with atomic layer deposition
Barrier layer produced with atomic layer deposition

Cross-section preparation of a barrier layer made of aluminium/titanium oxide nanolaminate

Surface and interface analysis at iMST deals with the investigation of the surface and layer morphology of a sample, i.e. the structural composition and the microstructure of a layer. In addition to roughness and step height, a chemical analysis of the surface and the area near the surface is also performed if required. Contamination of the surface, chemical composition of the near-surface area, or, for example, wettability as a result of surface activation can be investigated. In order to investigate the layer properties of the near-surface region, cross-sectional preparations are usually carried out. In the case of porous materials, for example, the pore size can also be determined in depth. Cross-section preparations are also used in particular for multilayer coatings (nanolaminates).

Analysis methods used include:

  • Light microscopy
  • Scanning electron microscopy with energy dispersive X-ray spectroscopy (EDX)
  • Transmission electron microscopy with EDX and electron energy loss spectroscopy
  • Atomic force microscopy
  • Contact angle measurement
  • Ellipsometry
  • Fourier transform infrared spectrometer

Especially for coatings with structure sizes in the nanometer or micrometer range, fundamental questions and validations of coating properties can be performed with these analysis capabilities. The following image shows a cross-sectional preparation of a barrier layer consisting of an alumina/titania nanolaminate prepared by atomic layer deposition (ALD). The image was taken in a transmission electron microscope.

Projects

Institute of Microsystems Technology (I26621-1)

The Institute of Microsystems Technology works with companies, scientific institutions and universities on application-oriented issues in numerous cooperation projects. The resulting projects use state-of-the-art technologies and contribute to current research questions in the field of microsystems technology.

The research institute also focuses on the technology transfer of acquired knowledge into practical applications.

Labs and equipment

The outstanding equipment at the Rottweil Study Center and the Technology Laboratory for Nano and Microsystems in Furtwangen are used at the Institute of Microsystems Technology.

Centrally, innovative plasma coating technologies are focused at the Rottweil study center. A fully developed silicon technology is operated in the technology laboratory for nano- and microsystems. This enables the processing of structures down to the nanometer range and the prototypical realisation of micro and nano systems.

For students

Project and thesis work

Project and thesis work

It is possible to write project work and your final theses at the institute on current projects and research topics. This is often linked to practical laboratory work. The writing of a project or final thesis enables the student to gain first insights into working in the field of research at an early stage of his or her professional career. Current calls for proposals and the corresponding contact persons can be found under Internal link opens in the same window:Services und Downloads.
For general questions about project and thesis work at iMST please contact:

Student assistant jobs

Student assistant jobs

To support current topics and tasks, positions as research assistants (Hiwi) are offered. The areas of responsibility can be wide-ranging and also include work in the laboratory. Current offers can be found under Internal link opens in the same window:Services und Downloads.

Practicals and lectures

Practicals and lectures

Several courses offered by Furtwangen University provide a basic knowledge of microsystems technology and ideal preparation for a professional career in this field. Students who are interested in microsystems technology are encouraged to seek information about the following courses:

  • Coating Technologies with practical (Prof. Dr. Volker Bucher, in the APE and MZ / MZT master programmes)
  • Intelligent implants in medicine (Prof. Dr. Volker Bucher, in the TP and MZ / MZT master's programmes)
  • Microfluidics (Prof. Dr. Stephan Messner, in the MZ / MZT master's programme)
  • Microsystems Engineering (Prof. Dr. Stephan Messner, compulsory subject in the bachelor program IME / WFT)
  • Microsystems Technology - Technologies and Applications (Prof. Dr. Stephan Messner, compulsory elective subject for Bachelor's programmes)
  • Plasma- / Thin film-Technology (Prof. Dr. Volker Bucher, elective subject in bachelor programmes, alternating between German and English)
  • Sensors and Actuators (Prof. Dr. Ulrich Mescheder, in ELA Bachelor's programme)
  • Sensors and Actuators (Prof. Dr. Ulrich Mescheder, in the SMA Master's programme)
  • Technologies for Microsystems and Microelectronics (Prof. Dr. Ulrich Mescheder, in the SMA and MTZ Master's programmes)

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Doctoral degrees

It's possible to go from bachelor's to master's to doctorate at Furtwangen University. It is also possible to do a doctorate at the Institute of Microsystems Technology. Currently, 6 doctoral students are conducting research at the institute, dealing with a wide variety of topics in their work, including sensor and actuator systems, coating processes and analyses, MEMS and functional surfaces.

Particularly close contacts for cooperation and supervision exist with the universities of Freiburg and Tübingen. Prof. Dr. Ulrich Mescheder is an associate professor at the Faculty of Engineering of the University of Freiburg and can therefore offer doctoral degrees.

Click here for details about taking External link opens in a new window:doctoral degrees at HFU.

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Publications

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